R: Biplot of Multivariate Data

biplot {stats}

R Documentation

Biplot of Multivariate Data

Description

Plot a biplot on the current graphics device.

Usage

biplot(x, ...)

## Default S3 method:
biplot(x, y, var.axes = TRUE, col, cex = rep(par("cex"), 2),
       xlabs = NULL, ylabs = NULL, expand = 1,
       xlim  = NULL, ylim  = NULL, arrow.len = 0.1,
       main = NULL, sub = NULL, xlab = NULL, ylab = NULL, ...)

Arguments

`x`	The `biplot`, a fitted object. For `biplot.default`, the first set of points (a two-column matrix), usually associated with observations.
`y`	The second set of points (a two-column matrix), usually associated with variables.
`var.axes`	If `TRUE` the second set of points have arrows representing them as (unscaled) axes.
`col`	A vector of length 2 giving the colours for the first and second set of points respectively (and the corresponding axes). If a single colour is specified it will be used for both sets. If missing the default colour is looked for in the `palette`: if there it and the next colour as used, otherwise the first two colours of the palette are used.
`cex`	The character expansion factor used for labelling the points. The labels can be of different sizes for the two sets by supplying a vector of length two.
`xlabs`	A vector of character strings to label the first set of points: the default is to use the row dimname of `x`, or `1:n` if the dimname is `NULL`.
`ylabs`	A vector of character strings to label the second set of points: the default is to use the row dimname of `y`, or `1:n` if the dimname is `NULL`.
`expand`	An expansion factor to apply when plotting the second set of points relative to the first. This can be used to tweak the scaling of the two sets to a physically comparable scale.
`arrow.len`	The length of the arrow heads on the axes plotted in `var.axes` is true. The arrow head can be suppressed by `arrow.len = 0`.
`xlim, ylim`	Limits for the x and y axes in the units of the first set of variables.
`main, sub, xlab, ylab, ...`	graphical parameters.

Details

A biplot is plot which aims to represent both the observations and variables of a matrix of multivariate data on the same plot. There are many variations on biplots (see the references) and perhaps the most widely used one is implemented by biplot.princomp. The function biplot.default merely provides the underlying code to plot two sets of variables on the same figure.

Graphical parameters can also be given to biplot: the size of xlabs and ylabs is controlled by cex.

Side Effects

a plot is produced on the current graphics device.

References

K. R. Gabriel (1971). The biplot graphical display of matrices with application to principal component analysis. Biometrika 58, 453–467.

J.C. Gower and D. J. Hand (1996). Biplots. Chapman & Hall.